1. Field of the Invention
The present invention relates to a heat exchanger used for retrieving heat energy from a high temperature fluid, such as waste gas discharged from an internal combustion engine.
2. Description of the Prior Art
An example of a heat exchanger for retreiving heat energy from a high temperature fluid is shown in Japanese patent publication number 59-225294 dated Dec. 18, 1984. Therein the heat exchanger includes a header, water jacket and heat conductive tubes all being separately made and thereafter assembled. Thus, it includes many connecting portions which must be sealed by the use of gaskets or by brazing so as to prevent fluid leakage.
Another example of prior art is shown in Japanese patent publication number 59-49447 dated Mar. 22, 1984. The heat exchanger is formed by use of a complex shape casting. During such manufacturing, gas may be generated which penetrates the wall of the heat exchanger and causes pin holes. This may lead to a fluid leakage through the pin holes.